In related arts, implementation of a highly accurate current sampling circuit is as shown in FIG. 1, the current sampling circuit includes a power transistor M1, sampling transistors M2 and M3, and a close loop negative feedback circuit consisting of an operational amplifier, a transistor M4 and resistors R1, R2; wherein R1=R2, I1 and I2 are bias currents providing a quiescent operating point of the close loop negative feedback circuit, and the gain of the close loop negative feedback circuit is:Afeedback=Aop·gm4Ro 
In the current sampling circuit as shown in FIG. 1, the current in the power transistor M1 is firstly mirrored into the sampling transistors M2 and M3, after passing through the close loop negative feedback circuit consisting of the operational amplifier, the transistor M4 and the resistors R1 and R2, the mirrored current is output as a sampling current. In the above current sampling circuit, the clamping effect of the operational amplifier is used to ensure that a first input voltage Vn is equal to a second input voltage Vp so that the output sampling current Iout is the same as the current flowing through the sampling transistors M2 and M3, thereby the current in the power transistor M1 can be sampled stably and accurately; if the current in the power transistor M1 changes direction, the output sampling current also changes direction, thereby implementing accurate sampling of current in both directions.
The current sampling scheme in the related arts has the following disadvantages: 1) it is disadvantageous for applications in large-scale circuits having a high integration density; 2) the current sampling circuit is not energy-saving due to its high power consumption.